What is the purpose of the concatenation? Date serial number 42969 (the value apparently in B1) corresponds to the date of Tuesday 22 August 2017. You should not need to concatenate "Tuesday" onto that serial number, since Excel already knows that it represents a Tuesday. I would just format B1 with a long date format that includes the weekday. If you are trying to store the same value in another cell, you could do =B1 and change the format to be a long date.

I would suggest reviewing something like this to understand how Excel stores and works with dates/times as serial numbers: http://www.cpearson.com/Excel/datetime.htm